[apparmor] security_path hooks for xattr

[John Johansen]

On 01/26/2012 04:45 AM, Miklos Szeredi wrote:
> Forwarding from an internal bug report:
> 
>    "AppArmor does not mediate the xattr system calls for confined processes.
> 
>    As a consequence, a confined process can cross the confinement privilege
>    boundary by reading or writing to extended attributes that the confined
>    task should not have access to. The restrictions for security and user
>    attributes read and write still apply according to DAC; however, this
>    does not comply with the claim of AppArmor to mediate fipe
>    operations. The use of extended attributes is very flexible, so that the
>    effect of a missing mediation can lead to false assumptions in
>    subsequent policy decisions (eCryptfs)."
> 
> AFAIU this boils down to missing security hooks in *xattr().
> 
> Would it be possible to add these hooks?
> 
right, this is something we lost when we moved to the security_path hooks and
while we have spent some time looking at the problem, we haven't addressed it
yet.  

New hooks would certainly be the easiest solution. I looked at it back when
I initially did the port, and considered proposing new hooks at the time, but
for various reasons it was decided to separate that from the main apparmor
submission, and I haven't had a chance to revisit this since.